The present invention concerns a system for temporarily immobilizing two bodies relative to each other in at least -one predetermined direction and, in particular, an immobilizing system which, when released, allows movement of great amplitude of one body relative to the other.
To be more precise, in certain fields such as placing satellites in orbit it is generally necessary to immobilize certain elements during launch and to restore their freedom of movement when in orbit. This applies in particular to tilting plates which, when in orbit, must have their facility for angular relative movement of great amplitude restored.
The use of jacks for this purpose has been considered. In addition to the facility of moving the plate relative to a fixed support, such as a fixed plate, jacks could also be used to immobilize the plate relative to the support during launch.
However, in the space field the skilled person is reluctant to use jacks, mainly for reasons of reliability.
Should a jack fail it is particularly difficult to carry out any repair or to use a back-up jack.
The above type of jack is also relatively bulky, in particular when it is necessary for the mobile plate to have a large range of relative angular movement.
The present invention aims to mitigate these drawbacks.
To this end it proposes a system for temporarily immobilizing two bodies relative to each other at least one way in a predetermined direction characterized in that it includes:
a first interface part adapted to cooperate with a first body; PA1 a second interface part adapted to cooperate with a second body; PA1 an immobilizing device adapted to cooperate with the interface parts to assure the temporary immobilization, and including a rupture area; PA1 a rupture member made of a shape memory alloy adapted to deform when heated to rupture the rupture area to free the second body to move relative to the first body; and PA1 heating device adapted to heat said rupture member above a critical temperature to cause the shape memory alloy to deform. PA1 one of the abutments transverse to said direction includes a plate extending in the receiving housing, transversely to said direction, in that said rupture area comprises a continuous thinner area of the plate defining an internal area against which abuts a longitudinal end of the rupture member and a peripheral area, said plate being supported in said receiving housing, in said immobilizing position, by the peripheral area; PA1 said immobilizing device further comprise a rod extending in said direction, said plate having a circular opening through which said rod passes, said rod having a screwthreaded end engaged in said opening, and a nut mounted on said screwthread, abutting against said plate. PA1 the other interface part is attached to said rod and has an abutment surface constituting the other transverse abutment against which abuts the second longitudinal end of the rupture member; PA1 the rod has a transverse plate in the vicinity of its end opposite said screwthreaded end, said transverse plate having an abutment surface constituting the other transverse abutment against which abuts the other longitudinal end of the rupture member, and a smooth part at said opposite end on which is engaged a circular opening in the other interface part; PA1 the receiving housing is delimited by a cylindrical wall having a shoulder transverse to the longitudinal-axis of said wall, said direction being coaxial with said axis, the holding system further comprising a tubular member received in the receiving housing and having an external annular abutment at one longitudinal end adapted to cooperate axially with said shoulder and an internal annular rim in the vicinity of its other longitudinal end, said rupture member consisting of a sleeve surrounding said rod, said rupture member and said rod being received in said tubular member so that said rupture member, when it deforms, abuts against said transverse plate and against said internal annular rim, said external annular abutment being, in the immobilizing position, clamped between the transverse plate and the shoulder on the tubular member; PA1 the rod also has a second transverse plate in the vicinity of its end opposite said screwthreaded end, the second transverse plate being adapted to abut against the internal annular rim of the tubular member on one side, the rod further having, in the vicinity of that side, a significant reduction in diameter constituting a second transverse rupture area and, in the vicinity of the other side, a screwthreaded second longitudinal end with which is engaged a screwthread of the other interface part; PA1 the heating device include a heating coil around said sleeve; PA1 the heating device include a second heating coil, the heating device being adapted to heat the rupture member by means of the second coil in the event of failure of said heating coil; PA1 said transverse plate is supported in said receiving housing by means of a rim having an external screwthread engaging a screwthread on the cylindrical wall of the housing; PA1 the spring return member includes at least one Coll spring disposed laterally between the tubular member and the cylindrical wall, said spring abutting longitudinally against the external annular abutment on the tubular member on the side of said abutment opposite that bearing against the transverse plate and against a wall of a lug housing the spring, transverse to the longitudinal axis; PA1 each of the interface parts is bolted to the corresponding body.
An immobilizing system of the above type is particularly reliable because the release of one body relative to the other is obtained by the action of the rupture member made of shape memory alloy. The only possible failure is that of the heating device, for which redundancy is particularly simple to provide.
For simplicity and convenience the rupture member is adapted to deform by expanding in the direction when heated.
In a preferred embodiment, the rupture member is disposed between two abutments transverse to the direction so that the rupture member, when it expands, loads the abutments in the direction tending to rupture the rupture area.
In accordance with one particularly advantageous aspect of the present invention, one interface part has a housing receiving a part of at least one of the immobilizing device, the immobilizing device being mounted at one end on the interface part with the receiving housing, moving between an immobilizing position before the rupture area ruptures in which said immobilizing device projects partially from the receiving housing and a retracted position within the receiving housing after the rupture area ruptures.
Because of the above features, after the rupture area ruptures, the second body is not only released relative to the first body but also has a great amplitude of movement relative to it by virtue of the retraction of the immobilizing device within the housing receiving the first interface part.
Retraction can be effected by gravity or, in an application that is advantageous in the space field, by release of potential energy, in particular by means of a spring return member.
In accordance with other preferred features, which an possibly be combined: